IO Wait very high and real IO speed is very low

[Marty Sweet]

Hi Tomas,

Could you provide the output of /var/log/kernel.log and /var/log/dmesg
and $ df -h and $ fdisk -l ?
When the problem occurs, can you also run $ ps aux ?

Once you have done this please post it on pastebin and send the link,
as there will be a few hundred lines.

Thanks,
Marty

On Fri, Feb 28, 2014 at 6:00 AM, Tang Jianwei <myhnet at gmail.com> wrote:
> Hi All,
>
>     recently I get a very weird problem from my Ubuntu Server 1204 LTS
> 64bit:
>     1. the write speed can reach 500MB/s when there is no other processes
> running
>     2. the write speed down to around 10MB/s when there are many other
> processes and meanwhile:
>             a. only very high usage from io wait
>             b. sys, user and all the other cpu usages are very low
>             c. the system load average can reach to 15 and even more higher
>
>     can any one give me some advice what is wrong with my system, and what I
> should to adjust in hardware/software?
>
>     the platform is:
>     MB: Intel S3240GPLC
>     CPU: I3-540
>     RAM: Kingston 4G ECC
>     Storage: LSI MegaRaid 9270-8i, Raid 5 with 5 drives + 1 spare, ForcedWB
> with no BBU
>     Drive: WD 3T
>
>
>     thank you very much.
>
>
> Best Regards
> Tomas
>
>
>
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-- 
Marty